#include <fstream>
#include <vector>
#define NMAX 100002

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, nr, nrc;
vector<int> G[NMAX];
vector<int> GT[NMAX];
vector<int> CTC[NMAX];
int postordine[NMAX];
bool uz[NMAX];
void citire();
void afisare();
void DFS(int x);
void DFST(int x);

int main()
{
    int i;
    citire();
    ///etapa I
    for (i=1; i<=n; i++)
        if (!uz[i]) DFS(i);
    ///etapa II
    ///uz[i]=1 pentru varfurile nevizitate in DFST
    ///0 altfel
    for (i=n; i>0; i--)
        if (uz[postordine[i]])
        {
            nrc++;
            DFST(postordine[i]);
        }
    afisare();
    return 0;
}

void citire()
{
    int i, x, y, m;
    fin>>n>>m;
    for (i=0; i<m; i++)
    {
        //arc
        fin>>x>>y;
        G[x].push_back(y);
        ///in graful transpus pun arcul (y,x)
        GT[y].push_back(x);
    }
}

void DFS(int x)
{
    int i;
    uz[x]=1;
    for (i=0; i<G[x].size(); i++)
        if (uz[G[x][i]]==0)
            DFS(G[x][i]);
    nr++;
    postordine[nr]=x;
}

void DFST(int x)
{
    int i;
    uz[x]=0;
    CTC[nrc].push_back(x);
    for (i=0; i<GT[x].size(); i++)
        if (uz[GT[x][i]])
            DFST(GT[x][i]);
}

void afisare()
{
    int i, j;
    fout<<nrc<<'\n';
    for (i=1; i<=nrc; i++)
    {
        for (j=0; j<CTC[i].size(); j++)
            fout<<CTC[i][j]<<' ';
        fout<<'\n';
    }
}